Add status command

[stefanmb]

Summary

• Add a status command that shows the partitioning state of a table (intermediate existence, partition count, mirroring triggers, whether the original is partitioned)
• Supports --json flag for machine-readable output

Test plan

• Unit tests added for the status command and new table helpers

🤖 Generated with Claude Code

[stefanmb]

Though it adds more code my preference was to delegate the actual logic to Table in order to maintain separation of concerns.

[mthadley]

Looks good!

Left a few comments, but no blockers. Only waiting to approve because I think you'll want to merge in master and reconcile the changes from #16.